Eye quality monitor for a 2R regenerator

• US 6,433,899 B1
• Filed: 12/15/1998
• Issued: 08/13/2002
• Est. Priority Date: 10/06/1998
• Status: Expired due to Term

• Current Assignee: Ciena Corporation
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Anslow, Peter Jeremy, Solheim, Alan Glen, Habel, Richard Achille
• Primary Examiner(s): Chan, Jason
• Assistant Examiner(s): Bello, Agustin
• Application Number:
  US09/210,812
• Time in Patent Office: 1,337 Days
• Field of Search: 359/177, 359/174-176, 359/110, 370/243, 370/246, 375/213, 375/214, 379/4
• US Class Current: 398/5
• CPC Class Codes: H04B 10/07953 Monitoring or measuring OSNR, BER or Q
• CPC Class Codes: H04B 10/0797 Monitoring line amplifier or line repeater equipment

Abstract

The method of monitoring the quality of an optical signal at the site of a 2R or 1R regenerator, without performing a clock recovery operation, is based on slicing the recovered voltage with a threshold voltage, manipulated according to a pattern, and averaging the output of the slicer. An eye diagram is simulated by a diagram representing the average voltage versus the threshold voltage.

Claims

1. A method of monitoring the quality of an optical signal at a regenerator site, without performing a clock recovery operation, comprising:

generating a threshold voltage V_TH to take a plurality of values according to a pattern;

applying said threshold voltage V_TH on a first input of a slicer, and applying an input voltage V_in on a second input of said slicer to obtain a slicer output voltage V_S, said input voltage V_in being an electrical equivalent of said optical signal;

for said plurality of threshold voltages, obtaining a corresponding plurality of associated parameters; and

processing all said associate parameters as a function of all said without requiring input from a clock recovery operation for said processing step.

2. A method of monitoring the quality of an optical signal at a regenerator site, without performing a clock recovery operation, comprising:

generating a threshold voltage V_TH to take a plurality of values according to a pattern;

applying said threshold voltage V_TH on a first input of a slicer, and applying an input voltage V_IN on a second input of said slicer to obtain a slicer output voltage V_S, said input voltage V_IN being an electrical equivalent of said optical signal;

for said plurality of threshold voltages, obtaining a corresponding plurality of associated parameters; and

processing all said associate parameters as a function of all said threshold without requiring input from a clock recovery operation for said processing step.

wherein said parameter is an associated average voltage providing the average value of said slicer output voltage V_S.

3. A method as claimed in claim 2, further comprising:

normalizing all said threshold voltages, and said associated average voltages with respect to the logic 1 level of said input voltage V_in;

plotting a V_AV−

V_TH diagram using said normalized threshold voltages and said normalized associated average voltages;

comparing said V_AV−

V_TH diagram with a reference V_AV−

V_TH diagram to distinguish the effect of the noise from the effect of the distortion on said optical signal.

4. A method as claimed in claim 2, wherein said step of generating comprises:

providing a maximum threshold voltage above the maximum value of said input voltage V_in for obtaining a long one'"'"'s value, and providing a minimum threshold voltage less than the minimum value of said input voltage V_in for obtaining a long zero'"'"'s value;

linearly increasing said threshold voltage from said minimum to said maximum threshold voltage; and

repeating said step of linearly increasing at predetermined intervals.

5. A method as claimed in claim 2, wherein said step of obtaining a corresponding plurality of associated average voltages comprises determining an associated average voltage for each value assumed by said threshold voltage.

6. A method as claimed in claim 5, wherein said step of processing comprises:

providing a reflected version of each said associated average voltage to obtain a corresponding plurality of reflected versions;

normalizing each said threshold voltage, said associated average voltage and said reflected version with respect to the logic 1 level of said input voltage V_in; and

for each threshold voltage, adding said normalized associated average voltage with said normalized reflected versions to obtain said simulated eye diagram.

7. A method as claimed in claim 6, further comprising:

providing a maximum threshold voltage above the maximum value of said input voltage V_in for obtaining a long one'"'"'s value, and providing a minimum threshold voltage less than the minimum value of said input voltage V_in for obtaining a long zero'"'"'s value; and

adding said long zero'"'"'s value and said long one'"'"'s value on said simulated eye diagram.

8. A method as claimed in claim 6, wherein said step of providing a reflected version comprises:

determining a maximum of said average voltage, and

determining said reflected version for said threshold voltage by ascertaining a symmetrical value for said associated average voltage with respect to said maximum average voltage.

9. A method as claimed in claim 2, wherein said threshold voltage V_TH is generated in a digital format, is converted to an analog format, and is applied on said first input of said slicer in said analog format.

10. A method of monitoring the quality of an optical signal at a regenerator site, without performing a clock recovery operation, comprising:

generating a threshold voltage V_TH to take a plurality of values according to a pattern;

applying said threshold voltage V_TH on a first input of a slicer, and applying an input voltage V_IN on a second input of said slicer to obtain a slicer output voltage V_S, said input voltage V_IN being an electrical equivalent of said optical signal;

for said plurality of threshold voltages, obtaining a corresponding plurality of associated parameters; and

processing all said associate parameters as a function of all said threshold without requiring input from a clock recovery operation for said processing step,

wherein said associated parameter is a count indicating the interval when said input voltage is above said threshold voltage.

11. An eye quality monitor for a data regenerator for providing a simulated eye diagram of an optical signal without performing a clock recovery operation, comprising:

a pattern generator for generating a threshold voltage V_TH according to a pattern;

a slicer, for receiving a said threshold voltage V_TH on a first input and an input voltage V_in on a second input, and generating a slicer output voltage V_S, said input voltage V_in being an electrical equivalent of said optical signal;

an average detector for providing an associated average voltage V_AV of said slicer output voltage V_S corresponding to said a threshold voltage V_TH; and

means for processing said average voltages V_AV, to simulate an without requiring input from a clock recovery operation for said processing step.

12. An eye quality monitor as claimed in claim 11, wherein said means for processing comprises:

a reflected version unit for providing a reflected version of each said associated average voltage to obtain a corresponding plurality of reflected versions; and

an add unit for adding a normalized value of said associated average voltage with a normalized value of said reflected version, for each threshold voltage, to obtain said simulated eye diagram.

13. A method of monitoring the quality of an optical signal at a regenerator site, without performing a clock recovery operation, comprising:

generating a threshold voltage V_TH to take a plurality of values according to a pattern;

applying said threshold voltage V_TH on a first input of a slicer, and applying an input voltage V_IN on a second input of said slicer to obtain a slicer output voltage V_S, said input voltage V_IN being an electrical equivalent of said optical signal;

for said plurality of threshold voltages, obtaining a corresponding plurality of associated parameters; and

processing all said associate parameters as a function of all said threshold voltages to simulate an eye diagram of said optical signal, without requiring input from a clock recovery operation for said processing step.